1. Field of the Invention
The invention relates generally to the configurations and methods of manufacturing semiconductor power devices. More particularly, this invention relates to a device configuration and method of manufacturing semiconductor power devices integrated with Schottky diode without requiring additional masks, for reducing the turn off time and the power losses.
2. Description of the Prior Art
There is a great demand for implementing a semiconductor power device by integrating the Schottky diode as an internal diode. Specifically, the HV MOSFET behaves like a P-i-N diode with a negative drain-to-source voltage Vds<0, due to the built-in body diode formed by the P+, P−, and N-epi as shown in FIG. 1A. A high level injection into the N− Epi region from the P-body regions, shown in FIG. 1A, causes large turn off time and losses. Furthermore, a high rate of current variation, i.e., a large di/dt, causes a voltage spike and reduces a “softness factor”S. However, in order to improve the performance of the HV-DMOS, there is a need to reduce the turn off time and losses, i.e., to reduce the reverse recovery charge (Qrr), recovery time (Trr), and to increase the softness factor S. A HV MOSFET when integrated with an internal Schottky diode improves the performance of the HV MOSFET by resolving these technical limitations.
In addition to the above-mentioned demand for implementing the semiconductor power device with an integrated Schottky diode, the semiconductor power devices are widely implemented in a power supply and motor control applications. The semiconductor power devices are often formed with a full bridge type of topology as shown in FIG. 1B. For this type of application, an internal diode is very advantageous to function as a free-wheeling diode. A high voltage MOSFET, a super-junction semiconductor power device, and IGBT devices when implemented for the power supply and motor control applications often suffer from the limitations of high Qrr and power loss. A semiconductor power device when integrating the Schottky diode as an internal diode can resolve these technical problems. However, conventional configurations and methods of manufacturing the semiconductor power devices usually require an additional mask to block an area in order to integrate the Schottky diode as an internal diode of the power device in that area. Production costs are adversely affected due to additional this mask requirement.
For all these reasons, there are great and urgent demands to improve the configurations and method of manufacturing the semiconductor power device to integrate with the Schottky diodes as an internal diode such that the above-discussed technical limitations and difficulties can be resolved.